The following error occurred converting from sym to double: Unable to convert expression containing symbolic variables into double array. Apply 'subs' function first to substitute values for variables.

Question

Safia OUALLAM 2020-11-1

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/633029-the-following-error-occurred-converting-from-sym-to-double-unable-to-convert-expression-containing

回答： Gouri Chennuru 2020-11-5

hello

i'm not an expert in matlab! when i run my code this error comes every time "The following error occurred converting from sym to double:

Unable to convert expression containing symbolic variables into double array. Apply 'subs' function first to substitute values for variables.

can anyone help me pleeeeeeese!

clear  
close all
clc
syms x y
format short
f(x,y)=100*(y-(x^2))^2+(x-1)^2;
%gradient de la fonction:
g1=diff(f,x);
g2=diff(f,y);
grad=gradient(f(x,y),[x,y]);
g(x,y)=gradient(f(x,y),[x,y]);
hess=hessian(f(x,y),[x,y]);
%donnees du probleme:
x0=[0,1];
x1=[0,1];
alphaint=1;
beta=0.1;
taux=0.3;
N=100;
xn=x0;
%calcul du point critique avec le gradient:
for i=1:N
    a=1;
    d=-inv(hess)*g(x0(1),x0(2))
    x0(1)=x0(1)+a*d(1);
    x0(2)=x0(2)+a*d(2);
end
xfinal0=x0
%lignes de niveau de la fonction et points solution:
 r=1:10;
fimplicit(f(x,y)==r)
grid on 
hold on
plot(0,0,'*');
plot(xfinal0(1),xfinal0(2),'*')
hold off